Lined tank and method of making



July 25, 1961 w. A. BRIGGS LINED TANK AND METHOD oF MAKING /N VENT OR.

ATTORNEYS.

United States Patent O 2 993 617 LINED TANK ANI) VMiarnon oF MAKING William A. Briggs, Palos Heights, Ill., assignor to Rheem Manufacturing Company, Chicago, Ill., a corporation of California Filed June 1, 1959, Ser. No. 817,192 4 Claims. (Cl. 220-63) This 'invention relates Ato a lined tank and method of making and more particularly to the manufacture and construction of metal lined hot water tanks for use in hot Water heaters and the like. Steel tanks lined with non-corrosive metals, such as copper or aluminum, are the most eflicient constructions known for use in domestic or commercial hot water units. In the manufacture of such tanks, it has been very dilicult to obtain a strong mechanical joint between the shell and cover without destroying the liner at the joint or without exposing the steel of the shell or'cover either directly or through solution in the joint tothe water in the tank. Any exposure of the steel or of a joint-comprising an alloy rich in iron to the water is unsatisfactory and will result not only in destruction of the joint, but also in fouling of the water in the tank. Similar difliculties have been encountered in joining central tubes extending through the tank to the covers.

It is one of the objects of the present invention to provide a lined tank and method of making which incorporates a continuous mechanically strong joint between the shelland cover with no interruption in the lining and which-can easily be manufactured on standard manufacturing equipment.

Another object is to provide a lined tank and method of making in which the shell and cover liners are exposed at the end of the Shell land are brazed together to define a bead engaging the end of the shell and the flange on the cover without substantially melting the shell or flange.

According to a feature of the invention, a'skirt may be fitted over the cover flange spaced from the end of the shell and secured to the cover flange and the end of the shell by the same brazing operation.

A further object is to provide a lined tank'and method of making in which a tube extending through an opening in the cover is secured thereto by brazing a liner on the cover to the outer'surf'ace of the tube.

In one preferred Vmethod according to the invention, the shell liner extends Vbeyond the end of the shell and is folded over Vinto engagement with it to hold the liner against displacement -or wrinkling when the cover is inserted into the lined shell.

The above and other objects and features -of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing, in which:

FIGURE 1 is a partial enlarged section through the shell and cover of a lined tank embodying the invention prior to brazing;

FIGURE 2 is a partial enlarged section illustrating the condition of the joint between the shell and the cover after brazing; and

FIGURES 3 through 6 are partial sections similar to FIGURE 1 illustrating alternative arrangements prior to brazing.

The invention, as shown in FIGURE 1, is applied to a hot water tank having a cylindrical steel shell open at one or both ends and which is lined with a non-corrosive metal liner 11. While various metals may be used for the liner, the preferred metals at present are copper or aluminum, although substantially any desired non-corrosive metal having a melting point lower than the melting point of the steel shell could be employed.

'I'he open end of the shell is closed by a cover indicated '2,993,617 Patented July 25, 1961 r. ICC

generally `at 12 having a dished central portion and a peripheral flange 13. In the form shown, the cover is provided with a central opening defined by an outwardly extending annular ange 14. The cover proper is formed of steel and is lined with a metal `liner 15 preferably of the `same metal as the shell liner 11, but in any event of a non-corrosive metal having a lower melting point than the melting point of steel and which is compatible with the metal of the shell liner 11.

The cover is inserted into the end of the shell, as shown in FIGURE l, with the ends of thee liners 11 and 1'5 projecting slightly beyond the end of the shell. As shown, the `cover liner 15 projects a slight distance farther than the shell liner 11.

To complete the joint between the shell and cover the liners are brazed together to dene a bead 16, as shown in FIGURE 2. Any desired commercial brazing process may be employed, including silver solder, copper brazing, or bronze brazing. Preferably, the brazing operation is penformed in the usual manner with a torch and a brazing rod which is fed into the llame to melt in with the liner material and to form the bead 16. The brazing operation is conducted at a temperature which will melt and weld the material of the liners and which cause the brazing metal to alloy t0 some extent with the steel of the shell and cover flange to form a secure mechanical joint therewith. The brazing temperature is such that the `steel of the 'shell and cover will not be melted to any substantial extent, although as shown in FIGURE 2 the bead may penetrate very slightly into the flange 13 and 'over the'cornerof the end of the shell. In the boundary layers, the material of the bead alloys with the steel of 'the'shell and flange to provide a very secure adhesion through which it will furnish the requisite mechanical strength. Also rbecause of the doming of the center portion of the cover any internal pressure thereon will tend to expand `the cover flange outward into tighter engagement with the shell and its liner to tighten rather than loosen 'the joint therebetween.

It has been found that with the brazing operation conducted as described, the `metall of the liners will be fused together to a point within the outer end of the shell approximately as indicated in FIGURE 2. Thus the only metal exposed to the Water Vin the tank is the pure metal of the liners with no possibility of water leaking through the fused joint therebetween and reaching over the raw steel of the shell or cover or any portion ofthe brazed joint comprising an alloy 4rich in iron. Corrosion of the joint and Ycontamination of the water Yare thereby positively prevented.

'Phe central openingin the cover may receive acenter tube 17 which, as shown in FIGURE l, is formed of steel and is provided with an outer covering or liner 18 of a metal similar to the metal of the liners 11 and 15. The tube is assembled in the center opening in the cover with the liners projecting slightly beyond the flange 14 to be brazed together in the form of a bead, indicated in dotted lines at 19. This brazing operation may be performed in the same way as the operation to form the bead 16 and when completed will define the same type of duidtight and mechanically strong joint. If the center tube 17 were made of a solid copper or aluminum, which might be desirable, the brazing operation could be performed in the same manner to secure the tube to the cover liner 15 and mechanically to the cover flange 14.

Instead of extending both liners beyond the end of the shell 10, as shown in FIGURE l, they could be terminated flush with the end of the shell 10, as shown in FIGURE 3. When the brazing is effected with this construction the liners will be fused together to a point within the end of the shell 10 and a bead 21 will be formed mechanically joining the shell and cover flange so that 3 the resulting construction would appear substantially identical to that shown in FIGURE 2.

In the further variation illustrated in FIGURE 4, the shell liner 11 is vextended beyond the end of the shell and is folded over against the end of the shell, as shown at 22. This feature serves to anchor the liner within the shell against accidental displacement by the cover and its liner when they are assembled in the shell. After assembly, the parts are brazed to define a bead, as shown in dotted lines at 23, with the resulting joint appearing substantially as shown in FIGURE 2.

FIGURE 5 illustrates a further feature of the invention wherein the liners 11 and 15 terminate iiush with each other beyond the end of the shell 10, but short of the end of the ange 13. An annular skirt 24 in which burner apparatus or similar devices may be mounted, is telescopically fitted over the projecting end of the ange 13 and abuts against the ends of the liners, as shown.

With the parts assembled, the liners may be brazed together between the end of the shell and the apron to dene a bead, as indicated in dotted lines at 25. In this way, the shell, cover and skirt are all assembled simultaneously in a single operation.

FIGURE 6 shows a further modification wherein the liners 11 and 15 project substantially beyond the end of the shell and the brazing operation results in the formation of a bead 26 at the end of the shell, but short of the projecting ends of the liners. This construction may provide a slightly higher mechanical strength than the other structures illustrated because the bead tends to be slightly larger and to cover a greater area of the flange 13, but is otherwise similar to the joint illustrated in detail in FIGURE 2.

While several embodiments of the invention have been shown and described herein, it will be understood that they are illustrative only and not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. A lined tank comprising a metal shell having a uniform internal surface and open at at least one end; a metal liner in the shell formed of a metal having aY lower melting point than the metal of the shell and extending at least to the open end of the shell, a metal cover iitting Vinto the open end of the shell and having a peripheral flange projecting beyond the open end of the shell, a metal liner over the inner side of the cover extending at least to the open end of the shell and formed of a metal having substantially the same melting point -as the shell liner, and a brazed joint fusing together the metal of the liners, the shell and the flange forming a bead integral with the liners, the end of the shell and the flange of the cover,the liners being fused together in an integral mass extending inwardly between the metal shell and Vthe cover ange.

2. A lined tank comprising a metal shell having a un- -forrn internal surface and open at at least one end, a metal liner in the shell vformed of a metal having a lower melting point than the metal of the shell and extending at least to the open end of the shell, a metal cover 'tting into the open end of the shell and having a peripheral ange projecting beyond the open end of the shell, a metal liner over -the inner side of the cover extending at least to the open end of the shell and formed of a metal having substantially the same melting point as the shell liner, a skirt fitting over the projecting flange and terminating in spaced relation to the end of the shell, and a brazed joint fusing together the metal of the liners at the open end of the shell and the ends of the shell and skirt and the side of the ange.

3. The method of making a lined tank which comprises assembling in a metal shell hav-ing a metal liner of lower melting point than the metal of the shell a anged metal cover having `a metal liner thereover of substantially the same melting point as the shell liner so that the cover flange projects beyond the end of the shell and the liners extend at least to the end of the shell, and brazing the liners at the end of the shell at a temperature sufcient to fuse the liners together and to fuse them with the metal of the shell and cover into an integral annular bead Without substantially melting the metal of the shell or cover, the liners being fused together in an integral mass extending inwardly between the metal shell and the cover flange.

y4. The method of making a lined tank which comprises assembling in a metal shell having a metal liner of lower melting point than the metal 0f the shell a anged metal cover having a metal liner thereover of substantially the same melting point -as the shell liner so that the cover flange projects beyond the end of the shell and the liners extend at least to the end of the shell, assembling a skirt over the projecting ilange with its end in spaced relation to the end of the shell, -and brazing the liners at the end of the shell and between the shell and skirt at a temperature to fuse the liners together and to fuse them with the metal of the shell, the cover and the skirt without substantially melting the shell, cover or skirt.

References Cited in the file 0f this patent UNITED STATES PATENTS Schoessow May 2l, 1957 

